Exploring a multiplex DNA methylation-based SNP typing method for body fluids identification: As a preliminary...

Area of Science:

• Forensic Science
• Genetics
• Molecular Biology

Background:

• Accurate identification of body fluid origin is crucial for forensic investigations and crime scene reconstruction.
• DNA methylation analysis presents a novel approach for distinguishing between different body fluid types.
• Simultaneous analysis of CpGs and single nucleotide polymorphisms (SNPs) offers an efficient method for body fluid identification.

Purpose of the Study:

• To develop and evaluate a multiplex DNA methylation-based SNP typing system for body fluid identification.
• To assess the specificity, sensitivity, and performance of the system in complex forensic scenarios, including mixtures and degraded samples.

Main Methods:

• Development of a multiplex system for simultaneous typing of DNA methylation markers and neighboring SNPs.
• Testing the system's specificity using known body fluid samples (semen, saliva, vaginal fluid).
• Evaluation of sensitivity and detectability in mixed body fluid samples and artificially degraded samples.

Main Results:

• Four semen-specific DNA methylation markers (SE1-4) demonstrated good specificity.
• Two markers, one for saliva (SA1) and one for vaginal fluid (VA3), showed sporadic cross-reactivity.
• The VA3 marker was exclusively found in female samples, suggesting potential for sexual identification.
• The multiplex system successfully amplified DNA from mixed and aged samples, proving its utility for forensic casework.

Conclusions:

• The developed multiplex DNA methylation-based SNP typing system is a reliable and suitable method for body fluid analysis in forensic investigations, particularly for mixed stains in the Han Chinese population.
• This approach enhances the ability to identify cellular origins from body fluids at crime scenes.
• The system's robustness with mixtures and degraded samples makes it a valuable tool for forensic sample analysis.